She has lived in this city her whole life. She can speak two languages. She can sing an opera. She knows how to fix a TV. But she doesn’t know which subway train to take to get downtown. The author most likely includes this information to help the reader infer that
Esperanza’s mother is a great singer.
Esperanza’s mother is not very smart.
Esperanza’s mother is delighted with city life.
Esperanza’s mother is not able to travel much.